The German published application DE 3416592 and European Patent Application EP 0134010 A1, fully incorporated herein by this reference, disclose a counting device which serves for the acquisition of processing requests directed to a sequential logic processing system and which effects a rejection of an appropriate portion of these processing requests based on the measure of a percentage transmitted thereto by a traffic measuring device. In an arrangement of this known type, therefore, a rejection percentage which can be set in the counting device provides that all processing requests are identically treated. Some of the incoming processing requests are accepted based on the measures of the rejection percentage, but others are rejected. Processing requests are caused by arrival of information in connection-associated switching devices which is to be processed. This information can be selection information as well as other switch identifiers serving for establishing connections and for maintaining connections. Processing requests are also caused by new seizures of subscriber lines and trunks. Such requests are output to information-processing, central or subcentral, sequential logic systems by connection-associated switching devices.
In comparison thereto, the German published application DE 3416074, fully incorporated herein by this reference, discloses discrimination of processing requests into a plurality of urgency categories. The disclosed arrangement includes a seizure rejection device which qualitatively marks seizures (new occupations) as to be accepted in part and as to be rejected in part based on values (percentages) prescribed therefore. In addition, an urgency evaluating auxiliary unit is provided which re-marks higher urgency occupations already marked to be rejected, as being still acceptable, and likewise re-marking occupations of lower urgency already marked as acceptable as to be rejected, carrying this marking out on the basis of urgency data which are associated with each occupation, whereby the sums of the occupations (occupations to be accepted or, respectively, rejected) remain unaltered.
While in the arrangement disclosed in DE 3416592 and EP 0134010 A1, processing requests are acquired in toto and some of them are marked as acceptable and some are marked as rejectable simply on a quantitative basis, in the arrangement disclosed in DE 3416074, a discrimination of the occupations and of the processing requests lying therein is provided based on the measure of urgency values so that the occupations or processing requests are rejected or accepted based on their respective degree of urgency. In practical terms, this means that the occupations or processing requests having a lower degree of urgency, i.e. having the lowest urgency values, are affected first by the rejection measures such that, given a correspondingly higher rejection percentage, the seizures or processing requests of a second degree of urgency, i.e. having a second lowest urgency value, are also subject to the rejection measures. Given a further rejection, the seizures or processing requests having an even higher urgency value are affected by the rejection measures, etc, until, finally, the rejection measures also affect the seizures for processing requests of a highest degree of urgency which, therefore, are respectively marked with a highest urgency value. When the various urgency values of processing requests therefore first relate to new seizures of subscribers, secondly relate to seizures incoming via trunk lines and, third, relate to occupations outgoing via trunk lines, then it is advantageous to prioritize the processing requests for occupations outgoing via trunks over those for occupations incoming via trunk lines and to, in turn, prioritize all these processing requests over those which result from new seizures of subscribers. These relationships and principles are treated in the German published application 33 11 900, (U.S. 4,564,725, issued Jan. 14, 1986). also fully incorporated herein by this reference.
The present invention relates to a circuit arrangement for telecommunications switching systems, particularly telephone switching systems, comprising: central and/or sub-central information-processing sequential logic systems having a limited call-handling capability with respect to the information processing capacity; traffic measuring devices for identifying the information-processing traffic load of a respective sequential logic system and for the recognition of information-processing traffic overloads caused by processing requests; and comprising request rejection devices, serving as a defense against such overloads, in which a critical limit value can be set based on the measure of the respectively identified information-processing traffic load. It is also provided that different types of processing requests have different urgency values individually assigned thereto, and which, on the basis of a respective comparison of the urgency value of each processing request to a critical limit value respectively, the arrangement assigns these an acceptance character or a rejection character when the urgency value is greater than or, respectively, lower than the critical limit value, and by way of which each of the processing requests for incoming information are supplied or not supplied to the sequential logic system for processing in accordance with the appertaining character which has been assigned, whereby processing requests having above-average urgency are taken into consideration with a certain priority over processing requests having below-average urgency with respect to their processing in the sequential logic system.
The critical limit value is therefore a controllable comparison basis. Upon arrival of each processing request, it serves as a measure for deciding the acceptance or rejection thereof in the specified manner. The urgency value associated with each processing request is compared to this limit value.
The urgency value is formed from the results of continuously-executed measurements relating to this sequential logic system which measure its information-processing traffic load. The magnitude of the urgency value corresponds to a percentage of processing requests to be rejected due to the respective momentary operating situation. This percentage is therefore all the higher the higher the traffic load.
In a known manner, the processing requests are not uniformly accepted or rejected. They are accepted or rejected based on the respective magnitude of each of the individual urgency values which, therefore, are respectively compared to the momentary limit value.
A circuit arrangement of this type may be derived from the German published application DE 34160374, referenced above. Given a heavier traffic load of the central sequential logic system due to processing requests, therefore, this circuit arrangement enables the same to be treated based on their respective urgency degree, i.e. to still accept some of them, but to reject the rest. The urgency degrees of the connection-associated switching devices have urgency values assigned thereto, the connection-associated switching devices, given a seizure of a connection-associated switching device, respectively associating these urgency values to the processing requests emitted to the appertaining information-processing sequential logic system. Depending on the critical limit value which is set in the request rejection device, the appertaining processing request is still accepted or is still rejected based on a comparison of the appertaining urgency value to the limit value and based on whether this appertaining processing request is of the one type or the other type, as set forth above.
The connection-associated switching devices can be subscriber line circuits and connector sets. The latter can be prioritized over the subscriber line circuits. Given a certain degree of traffic load, this would mean that processing requests which come from connector sets would still be accepted, but no processing requests coming from subscriber line circuits would, by contrast, be accepted. In addition, the connection-associated switching devices can also be discriminated based on more than two types and the urgency degrees assigned thereto can be correspondingly multiply graduated in the described manner.